diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Everything Else (http://www.diyaudio.com/forums/everything-else/)
-   -   DIY FM antenna, can it be better than radioshack junk? (http://www.diyaudio.com/forums/everything-else/58754-diy-fm-antenna-can-better-than-radioshack-junk.html)

homer09 8th June 2005 07:06 PM

DIY FM antenna, can it be better than radioshack junk?
 
Im looking for a good DIY FM antenna for my Yamaha t-1 tuner. Right now im using a dipole and it pulls strong signals very well. But, i want to catch 99.9 here in montreal, which is a notoriously difficult one to pull.

Right now, i could catch it in mono/narrow slighlty off-tuning it intentionally. If i hold my dipole vertically, i get a flickering stereo light. So this is fringe reception, i need a little boost to get some nice stereo here.

What are you guys using for indoor FM antennas? A DIY solution interests me. here is what i absolutely need:

- better gain than a standard dipole
- the smaller the better, dont want to have to move furniture for this :dead:
- something that doesnt need constant adjustment for each station

shoot away :D

dnsey 8th June 2005 08:56 PM

It's perfectly possible and not difficult or expensive to build your own antennas - a member of the amateur radio fraternity would probably be happy to help you with it - but I think you'll have to compromise in order to balance your requirements.
To achieve more gain, your antenna must be more directional. In the case of a Yagi array (the usual type for domestic FM), this is achieved by adding directors and reflectors, which increases the overall size of the antenna. The extra directionality will make it necessary to rotate the array to receive different transmitters.
The only option I can think of is a switched pair of dipoles, one of which is dedicated to your DX station, perhaps with a VHF amplifier added.
All sorts of designs have been tried - some of which use materials such as aluminium foil and cardboard, so cost virtually nothing - you can have a lot of fun experimenting once you grasp the theory.
Whatever you settle on, make sure that it's properly impedence matched to your feeder and tuner - a great deal of signal loss can be due to a mismatch here.
Good luck!

homer09 8th June 2005 09:04 PM

thanks for the ideas. can you give me more specific leads for me to get started on? my requirements were in order of importance, so i will sacrifice the last one. do you have a recommended antenna recipe?

impedence matching, can you explain further?

TwoSpoons 9th June 2005 03:50 AM

You'd better sacrifice #2 as well. Small antenna's won't get the performance as their aperture is smaller (=less power pickup).

The best result is going to be had by putting your antenna on the roof, and using low loss co-ax to feed your receiver. I'd assume your receiver input is 75 Ohm? So you need 75 ohm co-ax (RG-59 IIRC). If you use a folded dipole it will have a 300 ohm impedance, so you will want a 4:1 balun to connect to your coax.

homer09 9th June 2005 03:57 AM

Quote:

Originally posted by TwoSpoons
You'd better sacrifice #2 as well. Small antenna's won't get the performance as their aperture is smaller (=less power pickup).

The best result is going to be had by putting your antenna on the roof, and using low loss co-ax to feed your receiver. I'd assume your receiver input is 75 Ohm? So you need 75 ohm co-ax (RG-59 IIRC). If you use a folded dipole it will have a 300 ohm impedance, so you will want a 4:1 balun to connect to your coax.


it has to be an indoor solution, i dont have the liberty to pull coax into my room or mount things on the roof.

my tuner has boath 75 ohm and 300 ohm. which is best to use?

still looking for an indoor solution that beats a dipole...

TwoSpoons 9th June 2005 10:21 PM

A colinear dipole might help. Though it will need loading coils to get the size down.

Basically, though, you're stuffed if you want gain at 99MHz, and you want it inside. Any solution with gain at that frequency is going to be big - simple physics. After all, the wave length you're after is around 3 metres, so even a proper 1/2 wave dipole is going to be 1.5 metres long.

homer09 9th June 2005 10:38 PM

Quote:

Originally posted by TwoSpoons
A colinear dipole might help. Though it will need loading coils to get the size down.

Basically, though, you're stuffed if you want gain at 99MHz, and you want it inside. Any solution with gain at that frequency is going to be big - simple physics. After all, the wave length you're after is around 3 metres, so even a proper 1/2 wave dipole is going to be 1.5 metres long.


well if its big but concealable, i dont mind, i just dont want something that doesnt looks like those big roof top antennas in my room. i dont mind something the size of a standard dipole, only mine isnt performing for me.

do you have more info on colinear dipoles and how i would build one?

thanks for the help, appreaciate it

TwoSpoons 14th June 2005 12:14 AM

Would you mind accurately describing (or photographing!) what you have currently? It would help knowing where you are starting from, in order to get improvements.

mcs 14th June 2005 12:31 AM

Quote:

Originally posted by homer09
well if its big but concealable, i dont mind, i just dont want something that doesnt looks like those big roof top antennas in my room.
A good FM antenna will be big, and most likely look like one of the roof-top antennas...

But it could still be concealable if you make one yourself using thick copper wire instead of aluminium tubes - that way you could make it flat at least.

Best regards,

Mikkel C. Simonsen

homer09 14th June 2005 12:50 AM

2 Attachment(s)
Thanks dnsey,

Here is my current setup: i have this tuner:

http://www.fmtunerinfo.com/T-1.jpg

http://www.fmtunerinfo.com/T-1closeup.jpg

a write up for the t-1 is available here:

http://www.fmtunerinfo.com/yamaha.html

note: this tuner is much better already than a technics tuner i was using previously (techincs st-c03)


i took a pic of the back of the tuner, but it really isnt clear since my camera is very bad. It basically consists of a 75ohm input, a 300 ohm input and an AM antenna input. (the dipole is currently connected in the 300 ohm input)

Also is a picture of a standard dipole antenna you can buy at any electronics store for a few dollars.

my room is located on the second floor, close to a window.


All times are GMT. The time now is 11:47 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2